Cytotoxicity testing biocompatibility

Various standards and procedures exist for the evaluation of the biological and immunotoxicity response of an implant [81] from the point of view of biocompatibility. Acute toxicity screening and in vivo implantation tests are fundamental in this respect. Cytotoxicity testing to detect the biological activity of the material on a mammalian cell monolayer is often the first step in assessing biocompatibility of a device. An international standard on the biological evaluation... 

Evaluation of biocompatibility resulted chieflyfrom clinical experience (Boutin, 1972 Hulbert, Morrison and Klawitter, 1972 Griss etal., 1973 Griss, 1984 Mit-telmeier, Heisel and Schmitt, 1987) supported by in vitro cytotoxicity testing (for example Catelas etal., 1998 Nkamgueu etal., 2000, and many other contributors). 

As to the biomaterial for human tissue replacement, it is necessary to demonstrate if the material has any effect on the biological properties of the tissue. Bioceramics exhibit some possible toxic reactions due to metal ions leaching from the ceramics, resulting in the tissue dying or heavy reactions. In this experiment, cytotoxicity test, hemolysis test as well as skin irritation were conducted to value the biocompatibility of the porous AI2O3 ceramics. 

Biodistribution and safety assessment during preclinical development requires both in vitro and in vivo studies. Biocompatibility of nanoparticles can be determined by in vitro cytotoxicity testing on cell lines. In vitro studies also facilitate the revelation of biochemical mechanisms under controlled conditions not achievable by in vivo studies. The rationale underlying the selection of in vitro assays to provide meaningful efficacy and safety data on nanoparticle is detailed in the literature. However, it is in vivo biodistribution and toxicity studies that determine safety for clinical trials, and all preclinical characterization studies must necessarily include in vivo determination of a nanoparticles biodistribution and toxicity in animal tests. FDA provides detailed guidelines for biodistribution and safety assessment of drug formulations in vivo using animal models and specific consideration for nanoparticle samples are reviewed elsewhere. ... 

Details are given of the synthesis of biodegradable graft copolymers based on a backbone of polylactic acid grafted with short blocks of polyacrylamide. Emulsion and solution polymerisations were examined. Molecular structures were determined by proton NMR and FTIR and by DSC. Cytotoxicity tests were conducted to assess their biocompatibility. Preliminary results of their potential in controlled release technologies are reported. 17 refs. 

Marques et al. (2002) studied the biocompatibility of starch-based polymers. The materials used for this study were (i) a 50/50 (wt%) blend of cornstarch and ethylene vinyl alcohol (SEVA-C), (ii) SEVA-C reinforced with 30 % (wt) of hydroxyapatite, (iii) a 50/50 (wt%) blend of cornstarch and cellulose acetate (SCA), and (iv) SCA reinforced with 30 % (wt) of hydroxyapatite. In the composites the average size of 90 % of the HA particles was found to be below 6.5 mm. Cytotoxicity tests with the extract of the materials were performed in order to evaluate the presence and or release of toxic leachables and degradation products. Cell material interactions on the surface of the polymers were observed by scanning electron microscopy (SEM) and related to the materials formulations. The short-term effect of leachables from starch-based polymers was quantified by exposing L929 cell to the degradation products released by those materials after immersion in culture medium. 

A hybrid BCB-silicon neural implant with embedded microfluidic channels has been fabricated and tested in acute recordings [70]. A thin layer of silicon was used to add mechanical stiffness to the implant. The fabrication process is based on SOI technology, where the device layer of the wafer was the 2-, 5-, or 10-iim silicon backbone of the BCB structure. The microfluidic channels were made with a sacrificial photoresist layer. Cytotoxicity tests of BCB have demonstrated its biocompatibility in glial and fibroblast cell culture [71] and using brain slice culture [72]. A summary of several microfabricated thin-film electrodes is presented in Table 1. 

ISO 10993 standard family regulates the testing required for a determination of biocompatibility for tissue contact devices. Cytotoxicity testing is a basic requirement for the biocompatibility assessment. The cytotoxicity assay requires the elution of the sensor with physiological saline and the evaluation of the effect of the eluate on living cells. This can be critical for enzymes which are not properly immobilized, plasticizers in substrates or membrane layers, and the often-used reference electrode material silver/silver chloride. Also relevant for CGM sensors, but not addressed by the elution test, is the effect of the enzymatic reaction in the sensor in the absence of polarization of the sensor. First-generation sensors which... 

Although the initially reported tissue compatibility tests for subcutaneous implants of poly(BPA-iminocarbonate) were encouraging (41,42), it is doubtful whether this polymer will pass more stringent biocompatibility tests. In correspondence with the properties of most synthetic phenols, BPA is a known irritant and most recent results indicate that BPA is cytotoxic toward chick embryo fibroblasts in vitro (43). Thus, initial results indicate that poly(BPA-iminocarbonate) is a polymer with highly promising material properties, whose ultimate applicability as a biomaterial is questionable due to the possible toxicity of its monomeric building blocks. 

As mentioned previously (and discussed in detail in Sec. IX), contact lens products have specific guidelines that focus on compatibility with the contact lens and biocompatibility with the cornea and conjunctiva [75], These solutions are viewed as new medical devices and require testing with the contact lenses with which they are to be used. Tests include a 21-day ocular study in rabbits and employ the appropriate types of contact lenses with which they are to be used and may include the other solutions that might be used with the lens. Additional tests to evaluate cytotoxicity potential, acute toxicity, sensitization potential (allergenicity), and risks specific to the preparation are also required [75-77], These tests are sufficient to meet requirements in the majority of countries, though testing requirements for Japan are currently much more extensive. 

The tests for in vitro biocompatibility were performed on normal cells (Vero) and tumor cells (glioblastoma). No cytotoxicity was detected in cells (normal or tumor) cultured with red and white onion extracts at low concentrations (between 0% and 1%), the cell viability being aronnd 90%. At higher concentration, the viability decrease slowly at 80% (Fig. 41.4a). On the other hand, garlic extracts indnce toxicity both on normal and tnmor cells at very low concentrations (Fig. 41.4b). 

ISO 10993 standards for evaluating biocompatibility, ISO 10993-5, Biological evaluation of medical devices—Part 5 Tests for cytotoxicity in vitro methods. 

Adhesives used in medical devices are tested for their effect on cells (cytotoxicity), blood constituents (hemolysis), and adjacent tissues, and for overall systemic effect. Several classes of biocompatibility testing exist. Adhesive suppliers, however, generally test to the following guidelines that have been established for toxicological properties and biocompatibility ... 

Biocompatibility at the Cell Culture Level. The liquid components, MAP and catechol oxidase, and extracts of two solid crosslinked materials were tested for cell culture toxicity and growth inhibition. The evaluation of cell culture cytotoxicity in an agar overlay method detects the impact on cells of any freely... 

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